<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="UTF-8" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
    <title>Document</title>
    <script>
      var sum = function (a, b) {
        return a + b;
      };
      function add(getSum) {
        return getSum(20, 30);
      }
      var result = add(sum);
      console.log(result);
    </script>
  </head>
  <body></body>
</html>
